1. Field of the Invention
The present invention relates to a method of manufacturing lens-fitted photo film units and an apparatus therefor. In particular, the present invention relates to a method of making a film roll from a filmstrip that is withdrawn from a cartridge shell, and loading the film roll and the cartridge shell in a film roll chamber and a cartridge chamber of the lens-fitted photo film unit, and an apparatus therefor.
2. Background Arts
Lens-fitted photo film units, hereinafter referred to as film units, contain a film cartridge and have a simple exposure mechanism for taking photographs on a filmstrip of the film cartridge. The filmstrip is previously withdrawn from a cartridge shell and wound into a roll. The film roll and the cartridge shell are loaded in a film roll chamber and a cartridge chamber of the film unit respectively.
Japanese Laid-open Patent Application No. 7-219156 discloses a method of loading a film unit with a new type of film cartridge that contains a filmstrip fully inside a cartridge shell, and can advance the filmstrip to the outside of the cartridge shell in response to a spool being rotated in an unwinding direction. Hereinafter, this new type of film cartridge will be called a leader-advancing type film cartridge. The film loading method according to this prior art is comprised of a first process of advancing the filmstrip a predetermined length out of the cartridge shell by rotating the spool, a second process of winding the filmstrip into a roll by engaging a leading end of the filmstrip with a winding shaft and rotating the winding shaft, a third process of putting the film roll and the cartridge shell in the film roll chamber and the cartridge chamber respectively, and a fourth process of pulling the winding shaft out of the film roll after the rear cover is attached.
The first to fourth processes are carried out in the same place while holding the cartridge shell by the same device. Concretely, a film supply shaft and a winding shaft are placed at a distance that is adjusted to the spacing between the film roll chamber and the cartridge chamber, and the spool of the cartridge shell is engaged with the film supply shaft. By rotating the film supply shaft and hence the spool in the unwinding direction, the filmstrip is advanced out of the cartridge shell. After the leading end of the filmstrip is secured to the winding shaft, the winding shaft starts rotating to wind the filmstrip into a roll, whereas the film supply shaft gets idle. The film roll and the cartridge shell are put in the film roll chamber and the cartridge chamber of the film unit by moving the winding shaft and the film supply shaft while maintaining the spacing between the winding shaft and the film supply shaft.
To secure the leading end to the winding shaft, the leading end of the filmstrip is inserted in a slit of the winding shaft and, thereafter, wound around the winding shaft by rotating the winding shaft. If the leading end of the filmstrip protrudes from the slit, the leading end is bent as the filmstrip is wound tightly around the winding shaft. Since the filmstrip is designed to be fully rewound back into the cartridge shell in the film unit after the completion of exposure of all available frames, it is necessary to advance the exposed filmstrip out of the cartridge shell for development and printing. However, if the leading end of the filmstrip is bent, it is difficult to advance the filmstrip out of the cartridge shell. Therefore, it is important to position the leading end of the filmstrip within the slit of the winding shaft.
To advance the filmstrip by a predetermined length out of the cartridge shell, it is possible to detect the leading end of the filmstrip by a photo sensor. However, since the film leader advancing process and the film winding process are carried out in the same place, the photo sensor must be placed before or behind the winding shaft in the film advancing direction. It is possible to provide a pair of sensors before and behind the winding shaft in the film advancing direction in order to confirm that the leading end of the filmstrip is positioned inside the slit of the winding shaft. In any case, however, the spool of the film cartridge should be rotated with accuracy after the detection of the leading end of the filmstrip by any of the photo sensors in order to stop the leading end inside the slit of the winding shaft. It is also time consuming. Besides, the length of the filmstrip out of the cartridge shell can change after the fine adjustment to the slit, as the filmstrip can uncoil inside the cartridge shell due to its own resiliency.
In view of the foregoing, an object of the present invention is to provide a method of manufacturing a film unit containing a leader advancing type film cartridge, by which it is possible to advance the filmstrip a predetermined length out of the cartridge with accuracy in a short time before winding the filmstrip into a roll. Another object of the present invention is to provide an apparatus for manufacturing a film unit according to the method.
The present invention is to provide a method and an apparatus of manufacturing a film unit, which achieve an efficient and accurate film pre-winding and loading process.
To achieve the above object, a method of the present invention is comprised of the following steps:
advancing the filmstrip out of the cartridge shell by rotating the pool through a spool drive shaft;
stopping the spool drive shaft when the filmstrip is advanced a redetermined length out of the cartridge shell;
detecting a rotational position of the spool at the stop of the spool drive shaft based on a rotational position of the spool drive shaft;
disengaging the spool from the spool drive shaft while maintaining the rotational position of the spool and the advanced length of the filmstrip unchanged;
engaging the spool with a film supply shaft, after adjusting a rotational position of the film supply shaft to the rotational position of the spool;
securing the leading end of the filmstrip to a winding shaft when the spool is engaged with the film supply shaft;
withdrawing the filmstrip from the cartridge shell and winding the filmstrip into a roll by rotating the winding shaft; and
loading the roll of the filmstrip and the cartridge shell in the film roll chamber and the cartridge chamber of the film unit respectively.
A film unit manufacturing apparatus of the present invention is comprised of:
a film leader advancing device having a spool drive shaft and a film leading end detection device for detecting the leading end of the filmstrip, the film leader advancing device advancing the filmstrip out of the cartridge shell by rotating the spool that is engaged with the spool drive shaft and stopping the spool drive shaft when the film leading end detection device detects the leading end of the filmstrip at a predetermined position out of the cartridge shell;
a rotational position detecting device for detecting a rotational position of the spool at the stop of the spool drive shaft based on a rotational position of the spool drive shaft;
a transferring device for holding the cartridge shell and the leading end of the filmstrip, disengaging the spool from the spool drive shaft, engaging the spool with a film supply shaft and securing the leading end of the filmstrip to a winding shaft, while maintaining the rotational position of the spool and the advanced length of the filmstrip unchanged;
an adjusting device for adjusting a rotational position of the film supply shaft to the rotational position of the spool before the spool is engaged with the film supply shaft, with reference to an output signal from the rotational position detecting device;
a winding device for withdrawing the filmstrip from the cartridge shell and winding the filmstrip into a roll by rotating the winding shaft; and
a loading device for loading the roll of the filmstrip and the cartridge shell in the film roll chamber and the cartridge chamber of the film unit respectively.
Since the film advancing process are performed separately from the film winding process, it is unnecessary to provide a winding shaft in the film advancing process, so it is possible to place a film leading end detection device, such as a photo sensor, right at a position corresponding to the predetermined advanced length of the filmstrip out of the cartridge shell, where the leading end of the filmstrip will be positioned inside the slit of the winding shaft in the next film winding process.
According to a preferred embodiment, the method of the present invention further comprises the steps of setting a film winding wheel of the film unit in a predetermined rotational position, and adjusting a rotational position of the film supply shaft at the end of the film winding process to the predetermined rotational position of the film winding wheel.
Thereby, the spool of the cartridge shell is smoothly engaged with the film winding wheel in the loading process when the cartridge shell is loaded in the cartridge chamber.